Older Hydrothermal Alteration in the Yellowstone Caldera

智力上的优点。怀俄明州黄石国家公园的黄石河大峡谷暴露出300-400米垂直的热液蚀变火山岩，这些火山岩非常鲜为人知。沿峡谷的露头包含了黄石热液系统最古老的(化石)。公园中没有其他位置提供进入热液系统横截面的通道，峡谷中存在着了解其他地方无法进入的更深层次系统的潜力。黄石公园的活动温泉是众所周知的，作为以蒸汽为主的系统的表面表达，提供了一个模型，可以用来检验这里提出的研究结果。初步野外和实验室工作在峡谷壁上发现了酸性硫酸盐和碱性氯化物低温热液矿物组合。这些数据表明，在过去的某个时候，存在两种流体，类似于今天在活动系统中发现的两种流体。这里提出的研究将致力于基于沿流体静力沸腾曲线上升的流体中的沸腾来重建较老的热液系统的上部300-400米，将评估黄石热液系统的寿命，将研究较老的流体及其关系，并将评估随着时间的推移黄石系统中通过上层地壳的热液质量和能量通量。黄石公园每年都有数以百万计的人从世界各地前来参观。他们带着对公园地质奇观的极大兴趣和好奇心而来。黄石河大峡谷是公园里最受欢迎的景点之一，但关于峡谷变化的科学信息却很少。事实上，这个变化就是公园名字的来源。希望这里提出的研究结果将向公园的游客提供，以加强他们对塑造公园的地质过程及其周围世界的理解和欣赏。其他更广泛的影响包括应用于火山灾害、地热资源和成矿过程。

Intellectual merit. The Grand Canyon of the Yellowstone River, Yellowstone National Park, Wyoming, exposes 300-400 vertical meters of hydrothermally altered volcanic rocks that are very poorly known. The outcrops along the canyon contain the uppermost parts of the older (fossil) Yellowstone hydrothermal system. No other locations in the park provide access to cross-sections of the hydrothermal system, and the potential exists in the Canyon to learn about the deeper system that is elsewhere inaccessible. The active thermal springs at Yellowstone are well known, and as the surface expression of the vapor-dominated system, provide a model against which the results of the research proposed here can be tested. Preliminary field and laboratory work has found both acid-sulfate and alkali chloride epithermal mineral assemblages in the Canyon walls. These data suggest the presence of two fluids at some time in the past, analogous to the two fluids found in the active system today. The research proposed here will endeavor to provide a reconstruction of the upper 300-400 meters of the older hydrothermal system based on boiling in a fluid rising along the hydrostatic boiling curve, will evaluate the longevity ofthe Yellowstone hydrothermal system, will examine the older fluids and their relationships, and will assess hydrothermal mass and energy flux through the upper crust over time in the Yellowstone system.Broader Impacts. Yellowstone Park is visited by millions of people from around the world every year. They come with a great interest in and curiosity about the park's geologic wonders. The Grand Canyon of the Yellowstone River is one of the most popular sites in the park, yet very little scientific information about the alteration in the canyon is available. This alteration, in fact, is the source of the park's name. It is hoped that the results of the research proposed here will be made available to the park's visitors to enhance their understanding and appreciation of the geologic processes that have shaped the park, and the world around them. Additional broader impacts include applications to volcanic hazards, geothermal resources, and ore-forming processes.